A Virtual Impedance Scheme for Voltage Harmonics Suppression in Virtual Oscillator Controlled Islanded Microgrids

Virtual oscillator control (VOC) is a promising nonlinear grid-forming control for AC microgrids that has gained increasing interest. This paper unveiled the strong harmonics rejection capability of VOC. However, due to the inverter filter and feeder impedance, the voltage at the point of common coupling will still be distorted when feeding nonlinear loads. To resolve this issue, this paper proposes a frequency adaptive virtual impedance scheme that is compatible with VOC. The proposed control scheme can effectively attenuate the voltage harmonics across the microgrid distribution network and ensure proper harmonic power sharing. The theoretical analysis is validated by Opal-RT based hardware-in-the-loop (HIL) experimental results.